The invention concerns a compact-disk reader wherein the first index for the individual program blocks recorded on a compact disk is stored.
The article Zusammenstellen eines CD-Programms ("Compiling a CD Program"), pages 26-28, Funkschau 15 (Jul. 18, 1986) describes what data are recorded on a compact disk and how a compact-disk reader processes them.
Each compact disk has a table of contents of data that provide information about the number of program blocks recorded on the disk, their starting times, and the overall playing time of the disk. The individual program blocks are as a rule musical selections, although they can also represented spoken texts or soundtracks for films and slideshows. Although up to 99 program blocks can be recorded on one compact disk, disks of music usually contain nor more than 10 to 20 different selections.
The table of contents of a compact disk has the data format illustrated in FIG. 1. The first block, A0, contains the title of the first musical selection, the second block, A1, that of the last selection, and the third block, A2, the overall playing time. The following blocks, Dl-Dn, contain the starting times of the n individual selections recorded on the disk. Blocks A0. A1, A2, and D1-Dn are combined into a group, in which the table of contents of the disk is completely stored.
Since the total amount of memory available on the disk for the table of contents is in the lead-in track and is completely occupied by several of these directly adjacent groups, the data relating to the table of contents of the disk are stored multiply redundantly.
When the disk is played, the starting points Dl-Dn, which comprise most of the data stored in the table of contents when there are more than three selections, are employed to calculate the starting times of the individual selections.
As illustrated in FIG. 2, the disk's lead-in track ES is followed by a pause PE with a prescribed duration of two to three seconds. Pause PE is followed by the individual program blocks, the four selections B1, B2, B3, and B4 illustrated in FIG. 2 for example. The last program block, selection B4, is followed by a lead-out track AS. The individual program blocks can be separated by pauses of durations that are not standardized. Between the first program block B1 and the second program block B2 in FIG. 2 is a pause P1, and between second program block B2 and third program block B3 is a pause P2, whereas fourth program block B4 follows third program block B3 directly. Pause P1 can be longer for example than pause P2.
Each program block is identified with a number to differentiate it from the others. The number tells the compact-disk reader what program block its pick-up is scanning at any moment. Furthermore, each program block has at least one and no more than 99 indices that can be employed to divide the block into up to 99 sections of any length. The indices for one program block extend from 01 to 99 and from 00 to 99 when there is a pause between two blocks. The index 00 is always assigned to a pause.
In FIG. 2 for example first program block B1 has only one index, 01, second program block B2 is divided into three sections by indices 01, 02, and 03 and third program block B3 into two sections by indices 01 and 02, and fourth program block B4 also has only one index, 01.
The total disk-playing time from the end of lead-in track ES to the end of lead-out track AS is stored parallel. The playing time of the individual program block is similarly stored inside each block, starting with time t=0. Stored parallel with each pause between two program blocks is the length of the pause, beginning, however, with the length of the pause at the start of the pause and ending at the end of the pause with the value zero. At this point the time is counted backwards as with a countdown, and the following four items of information are accordingly available to the compact-disk reader at the very instant its beam of light is scanning a location within a program block:
the playing time elapsed between the end of lead-in track ES and the location in question,
the time elapsed between the beginning of the program block and the location in question,
the number of the program block, and
the index assigned to the location in question.
If the scanning beam strikes a pause between two program blocks, the following three items of information are available:
the index 00, indicating a pause,
the playing time elapsed between the end of lead-in track ES and the particular location in the pause, and
how long the pause still has to go or, in other words, after how many seconds the next program block will begin.
The potential for dividing a program block into up to 99 indices a special advantage for longer musical selections or literary works. The compact-disk manufacturer can for example use the indices to specify the solos--piano solos or solos by a particular singer, arias, duets, or choruses in an opera. In works of literature they can indicate monologues or dialogues by particular persons for example.